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increase a psu voltage

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thebadtall

thebadtall

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Hello again !

This time, I'd like to double my PSU's voltage. Its a typical total 500w PC PSU with 3.3, 5 and 12 volt.

I would like to double the 12v to 24v in order to feed a small wattage class A amplifier, or just to try... (and the filter it)

I would not like to use a transformer, because I cannot find some, I cannot find also Chokes....
So I d like some suggestions with diodes and capacitors.

Also I had in mind to connect the 12v out of 2 psu's in series to check if they give 24v, (wich i find impossible)

Thank you !
 

Dear thebadtall
Hi
If you don't need high currents , you can use a voltage doubler with 2 diodes and capacitors easily . but if you need higher currents , you can use a simple boost converter . for boost converter you can use a simple LM2577 . you can increase it's out put power , with an external mosfet and an opto coupler , as high as you need ! .
Best Wishes
Goldsmith
 
Last edited:
You can connect two 12V PSUs in series to make a 24V PSU but you will probably have to change the grounding.

For example, lets say you have two 12V PSUs and both of them have the negative terminal connected to safety ground. When you connect the positive terminal of PSU A to the negative terminal of PSU B, you are short circuiting PSU A because now both it's positive and negative output terminals are connected to ground. The way to avoid that is to disconnect the ground from one of the PSUs.
 
It should be possible to modify the power supply to double the output voltage. The KA7500. controller is typically a derivative of a TL494 voltage mode controller with dual switching outputs. In order to do this some extra components are required for this modification :
-4 x 100V to 200V fast rectifiers diodes, (4A to 10A current)
-two 1000uF/ 50V electrolytic capacitors , low ESR type
-variable resistors 22k-100k, fixed resistors, 1k to 47k (depends on circuit).

Need to cut the grounded center tap on the low voltage secondary and to mount the fast rectifier diodes. The ATX PSU have a minimum output load requirement for them to start up. Not loading the outputs up enough will cause the power supply to turn on only briefly and then go back into standby.

More details here:

https://320volt.com/en/akim-voltaj-ayarli-atx-smps-guc-kaynagi-modifiye/comment-page-4/


Remember, we are dealing here with High Voltage and Line Powered Equipment so you should not try to modify an ATX power supply unless you understand the risks involved ! .



tl494-modiye-atx-smps-devre-semasi.jpg
 
dear sir MrRF, Id like to thank you for your help. however I would not like to disassemble a good psu, as it still is in waranty.

dear godfreyl, in order to unplug the ground It is necessary to open the psu, unfortunatelly, I dont want yet to harm the waranty

friend goldsmith, i d like to use diodes & caps. Id need a total of 30 watts,so i guess im goin 2 make many parallel circuits!
can you describe somehow the circuit?

(however, Ive ordered a 12 to 24v 200w from ebay...)
 

Dear thebadtall
Hi my friend
May i ask why not a boost converter as i suggested , too ? it will be simpler i think . i can help you to build it , if you want .
Best Wishes
Goldsmith ;-)
 
sure, no problem at all if only it will not use coils,transformers and chokes !!
 

It will use an small coil ! why you hate coils and transformers ? don't forget that high frequency coils and transformers are pretty small !
 
@thebadtall

In order to manually turn on an ATX power supply we only need to pull the PS_ON pins (for each unit) to the ground. Conveniently, the PS_ON pin(the green wire) has two GND pins next to it on the same row, so we need to connect the green wire to a black wire. This can be done with a small piece of wire.

Need to mention also one important thing.
By connecting series the two power supply units to obtain an 24V output, one of the chassis remain connected to the +12V of the second unit, so you need to keep the two power supply units chassis separated, see the attached diagram.
 

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    ATX series units.jpg
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Oops... Need to connect the yellow cable = +12V, not the red wire (as I have connected in the attached picture)
Red wire = +5V only…
:-D
 

You already have 24V in any ATX PSU.. Any modifications to PSU will void warranty. Most PSU's need a 10% pre-load of rated current on main supply to keep it stable but if already connected to your PC, just tap into the +12 and -12V pins. If standalone.. dont forget to jumper the POWER On to ground.

Screen shot 2012-06-05 at 8.48.13 PM.PNG
 

sunnySkyGuy, in the atx psu there is not a single 24 v supply,as far as i know. do you mean if i connect 2 seperate 12 v of one psu, or you mean something else?

mrRf why the-12v is not enough? is that because the psu is switching? The amp is low power, about 2x8w class a, i guess it will consume around 60w
 

There a solution for a limited power to use the -12V and the +12V pins, also do not to connect the chassis in the new circuit. In this way you may obtain a 24V output (limited current as the -12V output circuit.)
:-D
 

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